This invention relates to an automatic frequency and gain control circuit utilized in the receiving apparatus in a ground station for satellite communication.
An automatic frequency control (AFC) and automatic gain control (AGC) circuit (hereinafter referred to AFC/AGC circuit) is provided for the receiving apparatus in a ground station for satellite communication. The purpose of the AFC/AGC circuit is to detect a frequency deviation and a level variation of a received reference signal, that is, a pilot signal and to supply the detected deviation and level variation to a demodulator. These AFC and AGC circuits have been constructed as analogue control circuits.
As will be described later in detail, the analog AFC/AGC circuit has various problems including misoperation of a reference signal detector and incapability of effecting desired sweeping.